Glower for incandescent lamps.



Pa tented Oct. 8, I901.

Mi W. HANKS.

GLOWEB FOB INGANDESGENT LAMPS.

(Application filed In. 94, 1899.\

(lo Iodol.)

Y ucnms vsrzn: co. moraumow Msnmm'on o c UNiTED STATES PATENT Geri-cs,

MARSHALL WV. HANKS, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO GEORGE WESTINGHOUSE, OF SAME PLACE.

GLOWER FOR INCANDESCENT LAMPS.

SPECIFICATION forming part of Letters latent No. 684,229, dated October 8, 1901.

Application filed March 24, 1899.

To all whom it may concern:

Be it known that I, MARsEALL W. HANKS, a citizen of the United States of America, and a resident of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Glowers for Incandescent Lamps, of which the following is a specification.

My invention relates to the class of electric lighting devices in which the illuminant or glower is composed of certain refractory materials which are classed as non-conductors of electricitywhen cold, but become conductors when sufficiently heated.

The object of my invention is to so shape the glower of such electric lighting devices as without the sacrifice of strength to afford the largest practicable amount of light emitting surface.

It has heretofore been proposed to form glowers of this class from-mixtures of rare earths suitably ground and shaped into thin cylindrical pencils or rods. Ihave discovered that by forming the material into thin strips having an approximately uniform thickness and having difierent portions lying in different planes a greater amount of light can be obtained from a given flow of electric current than is secured when the glowers are circular in cross-section. For example, I have successfully demonstrated this fact by using glowers having a semicylindrical or a U-shaped cross -section or a cross section shaped like an X or a -l-. When the crossshaped section is employed, the glower is found to have a greater strength per unit cross-section than glowers of the rod orcylindrical form.

The superior light-giving capacity of the glowers above described is believed to be due to the fact that in such glowers the thickness is practically the same in all portions, and a more even distribution of the current through the glower is thus effected. This is of importance, because the conductivity of the material increases with the increase of temperature, and hence there is a tendency for the current to fiow in greater volume through the most heated portions of the glower. In

a cylindrical body the central portion, being most remote from the surfaces of radiation,

Serial No. 710,313. (F0 model.)

becomes most highly heated, and therefore the best conducting portion, whereas, on the other hand, the emission of light from the central part is interfered with and largely prevented by the presence of the exterior portions. It is thought that another reason for this greater efliciency of a glower having, say, a U-shaped cross-section is that the radiation of heat from the inner surface of the U is not so great per unit area asfrom the outer surface of cylindrical form, and consequently the inner surface of the U is the hottest, and so has the greater current density, which means more light. Since the cross-shaped glower is simply four U-shaped glowers put together back to back, the same state of things exist with respect to it as with respect to the glower having a U-shaped cross-section.

In the accompanying drawings, Figure l is Y an enlarged longitudinal view, and Fig. 2 is an enlarged cross-section, of a glower constructed in accordance with my invention. Figs. 3, 4, and 5 are enlarged cross-sections illustrating modified forms of my invention. Referring to the drawings, A represents a glower of U-shaped cross-section, the said glower being provided with suitable leadingin wires or a, of platinum or other suitable material. The glower is shown in cross-section in Fig. 2, being formed with a longitudinal groove 1) approximately semicircular in shape. The glower at its central portion may be described as of an inverted-U shape or as having a semicircular or other form, the edges of its arms a a lying in diiferent planes from its central portion. By U -shaped I do not wish to be understood as meaning a construction in which the body of the material is necessarily cut away to so great an extent as represented by the letter U, for the glower may be simply grooved and the thickness of the body may be only approximately uniform.

In Fig. 3 the glower is shown as having four longitudinal grooves b b b b being of an X-shaped cross-section and having four arms a a a a shape as to form a Greek cross with four arms a a 0. a. In Fig. 5 two grooves are shown, the glower being of a T-shaped cross section. Other slight modifications in the In Fig. 4 the grooves are of such shape of the glow'er may be made without departing from the spirit of my invention. Curved or bent shapes which permit of the glowers having approximately uniform thickness throughout are in line with it.

I usually enlarge the ends of the glower to which the leading-in wires a are attached, as shown at c c in Fig. 1. The enlargements may take any desired form; but usually they are somewhat of a spherical contour.

I claim as my invention- 1. A glower which is a conductor of electricity only when hot and which has one or more longitudinal grooves, and is of substantially uniform thickness, the main radiatingsurfaces of the said glower being similarly curved.

2. A glower which is a non-conductor when cold and a conductor when hot and is provided with one or more longitudinal grooves the bottom or bottoms of which are curved, V

the cross-section of the said glower being of approximately uniform thickness and the edges formed by the groove or grooves being rounded as described.

3. A glower which is a non-conductor ,when

cold and a conductor when hot and has a body j portion of U shape in cross-section and of substantially uniform thickness.

4:. A glower which is a non-conductor when cold and a conductor when hot and comprises a body portion of U shape in cross-section 

